Brake slack adjuster



`Maly 2z, 1951 AFSHIELDS l 2,554,064

BRAKE SLACK ADJUSTER Filed July ll, 1947 I 2 Sheets-Sheet 1 atented May 22, l195i BRAKE SLACK ADJUSTER Albert F. Shields, Forest Hills, N. Y., assigner to Sier-Bath Gear & Pump Co., Inc., North Bergen, N. a corporation of New Jersey Application July 11, 1947, Serial No. 760,416

8 Claims. l

The invention relates in general to an automatic slack adjuster for fluid pressure brakes and particularly relates to adjusting mechanism for use on automatic vehicle brakes in which slack in the brake operating mechanism is automatically adjusted in response to the usual brake mechanism, moving beyond its predetermined range of normal operation.

It has been known in this art to incorporate a slack adjuster or wear compensating mechanism in and as part of th-e usual brake applying mechanism so that an over-travel of such mechanism in its normal operation will re-adjust the brake applying mechanism in such way as will compensate automatically for wear in the operative elements of the brake applying mechanism.

These known devices have not proven entirely satisfactory in actual service particularly when installed on automotive vehicles, among other reasons mainly because they were unsafe. The parts thereof which form the wear compensating means is an integral part of the brake applying mechanism and thus a failure in their automatic slack adjuster feature would mean a complete brake failure. Further in these known devices they automatic adjuster elements are quite apt to function accidentally due to their interlocking features; to make, or at least attempt to make, an adjustment when not needed; elements were often used which could not withstand the vibration and rough usage to which normal operation would subject them, and in general suchdevices are so complicated in structure and operation as to render their use too expensive vand in many cases not entirely suited for their intended purpose.

Accordingly, the primary object of the invention is to provide a simple form of slack adjuster which is supplemental to and thus can be regarded as an addition or an attachment to any usual form of brake actuating mechanism otherwise complete per se, and which'attachment can be added as a separate unit to known form of wheel-brake actuating mechanism. disclosure features brake wearing compensating mechanism which will normally be inactive and,

thus removedfrom any possibility of Vpartaking In general in the usual braking operation and which will come into operation only when the power generating element of the conventional brake apply-- ing mechanism moves over an excessive range of travel in its effect to cause the desired clutching action of the brakes.

Various other objects and advantages of the irlvention will be in part obvious from a consideration of the method features of the disclosure and from an inspection of the accompanying drawing and in part will be more fully set forth in the following particular description of one method of practicing the invention, and the invention also consists in certain new and novel modifications of the preferred method (and other features of construction and combination of parts) hereinafter set forth and claimed.

In the accompanying drawings:

Fig. 1 is a View partly in vertical transverse section of a wheel brake drum," associated shoes and their operating cam, and partly in section showing an attachment thereto constituting a preferred embodiment of the invention and taken on the broken line I-I of Fig. 2;

Fig. 2 is an enlarged view in side elevation of the device shown in Fig. l;

Fig. 3 is an enlarged view, largely in side elevation and with parts broken away of the brake actuating device shown in the preceding figures and;

Fig. 4 is a longitudinal sectional view taken on the horizontal plane indicated by the line 4 4 of Fig. 3 with the parts of both Figs. 3 and 4 shown in their normal in-operative non-braking position.

In the drawings and referring rst to conventional vehicle wheel-brake parts (illustrated in Figs. 1 and 2) there is shown an axle housing A containing a wheel driving axle B for turning wheel C and associated brake drum D. Mounted within the drum is a pair of distendible .brake shoes E with an actuating double lobe cam F between their free ends and which free ends are held in engagement with the opposite long sides of the cam by a spring G. The cam is actuated by a cam shaft H mounted in bearing I in the form of a boss J projecting from a rear face plate K carried by the axle housing A and closing the rear side of the drum D, all as is used with a known type of vehicle wheel-brake.

Referring first to the mechanism which operates the cam F to distend the shoes E and thus cause the brake to function there is disclosed a source of power'in this particular case shown to be of the compressed air actuated wheel-brake type. The power originates in two-part pressure containing casing lil secured to the axle housing and between which two parts is clamped a freely swinging diaphragm Il. Compressed air is admitted conventionally to one side of the diaphragm through a tapped inlet l2.

A long main cam operating plunger I3 is slidably mounted in suitable bearing provided therefore in the casing IIJ for reciprocating movement and at its inner end has a broad disk-like head I4 secured to and movable with the central portion of the diaphragm. In normal operation the diaphragm has a relatively short amplitude of swing at its center, say of sufcient extent to move the head I4 from the solid line position to the dotted line position of Fig. 4.

The plunger I3 extends through the side of the casing I6 nearest the cam shaft and has this end threaded in the portion thereof which extends exteriorly of the casing.

A clevis forming fork I5 is in adjustable threaded engagement with the projecting portion of the plunger as best shown in Fig. 4. An accordion I6 fitted to the casing and plunger duefeats entrance of water or dirt to the interior of the casing through the opening in which the plunger slides. An operating arm II is provided with an enlarged head I8 considered for the moment as secured to the cam shaft l-I to rock the same. A reduced end I9 of the arm has its free end fitted between the bifurcations of the fork I5 and is pivoted thereto by pivot pin 28.

In operation, actuating air pressure admitted to the right side of the diaphragm when in the full line position shown in Fig. 4 will swing the center of the diaphragm and with it the plunger head I4 from right to left as indicated by the arrow a distance, say that measured between the full lineV and dotted line position of the plunger head. This action will cause the plunger I3 to shift the arm Il in a clockwise direction from its normal position shown in Fig. 3 for adistance sufficient to act through the cam shaft H, and shift the cam F from the position shown in Fig. 1 into such angled position as will move the brake shoes EV outwardlyv into a braking engagement with the brake drum as is usual in such cases. Releasing air pressure will permit 0r cause the brake actuating mechanism to return to its normal inoperative position by means forming no part of this disclosure of the brake actuating mechanism. A powerful return spring 2 I` isshown in Fig. 4 biased to return all parts to their normal inoperative position is suggested as one such means.

Referring now to the earnr adjustingy mechanism herein featured there is disclosed atv the casing II) a supplemental index mechanism containing casing 22 tted to the casing I8 and secured thereto through outstanding flanges 23and screws 24. Mounted within the casing 22. is cam indexing mechanism which includes an indexing plunger 25v slidably mounted for reciprocating movement in a guiding tube 26 provided therefore as part of the casing 22. The inner end of the plunger 25 is provided with a small pressure head 2'I located within the casing I8 and disposed in the pathof movement of the plunger head I4. It is a feature of this disclosure that the head 2'I of the indexing mechanism is normally spaced from and thus completely independent of the normal amplitude of swing of the head I4, except in those cases where an excessive movement of the head I4 causes it to bear on and thus shift the indexing plunger as a whole to the left of the showing in Fig. 4. The plunger 25 is backed by a strong return spring 28 biased to move the plunger towards its normal position shown in Fig. 4, opposing displacement of the same by the diaphragm. A pin 44 in tube 26 is arranged to engage a groove in the sliding-plunger 25 so that its return movement through action of spring 28 will be limited.

A ratchet wheel 29 of the one-way toothed type is secured to a shaft 38 journalled in the casing 22 and is engaged by a feed pawl 3l pivoted at its right end to the indexing plunger 25 and with its multiple toothed left end 32 maintained in racking engagement with the teeth of the wheel 29 by means of a small contact spring 33. A locking pawl 34 through compression of a small spring 35 engages the ratchet wheel 29, to defeat clockwise retreat of the ratchet wheel. A flexible drive shaft casing 36 leads from one end of the housing 22 to the head I8 of the rocking arm I'I.`

Within the casing 36 a flexible drive shaft 45 g connects ratchet shaft 38 with a worm shaft i2 journalled in the head I8. Within a recess 3l provided therefore in one face of the head I8 is av large worm gear 38, splined to the cam shaft H as shown in Fig. 3. 'I'he worm gear is engaged by a worm 39 carried on a worm shaft 48 journalled in the` head I8. A second worm gear 4I is secured tor one end of the shaft 46 and this in turn is driven from a worm shaft 42 to the, protruding endl of which (not shown) an end of the flexible shaftA 45 is secured. A cover plate 43 closes the recess 31.

The flexible shaft, of course,y maintains the cam shaft I-Il under control of the indexing mechanism in all operative positions of the arm Il as it swings back and forth in the normal operation of applying the brakes.

In operation and assuming that in operating the mechanism to cause the brake to function the plunger 25 is shifted a distance equal to say one tooth distance on the ratchet wheel 29 at the samey time the return spring 28 will, of course, be placed under compression. The feed pawl 3i will mover its toothed end 32 idly past the previously engaged teeth of the wheel 29; at which time the pawl 34 will be operative to hold the ratchet wheel 29 from turning. When the actuating', pressure is released from the indexing plunger head 21, the spring 2S reasserts itself and bears4 on the plunger 25 to shift it from left to right back into its initial and normal positionv limited by the pin and slot stop at 44. At

the same time the toothed end 32 of the feed pawl 3l engaging an advanced set of teeth on the ratchetwheelY 29v and rotates the same counter-clockwise over a small arcA and which movement is permitted by the locking pawl 34.

The turning or indexing movement of the ratchet wheel 2,9is transmitted through the Worm gear drive formed of, the connected parts 42, 4I, 48, 39 and 38 to turn the cam Il suflicient to take up. any wear which may have occurred between the cam, the shoes and the brake drum. In this way the brake operating parts are restored to their intendedoperative condition even though they cam H and associated, parts have become wornm use.

It is particularly notedthat the cam is under controloftwo independent chainsA of connected parts. For the no rmal operation ofthe brake, the push o f thediaphragm operatesdirectly through plunger I3, fork.l5-, arm II, relatively fixed-.worm 39-andworm gear 38 in this casey acting as alock between the arm I'I andthe cam shaft H, to actuate thecam somewhat following conventional practices inthis respect. rIhis brake controlling operation can-.be hadfeven if the indexing mechanism is absent or inoperative-for` any reason.

The other chain of connected parts operatesto index,- inidistinctionfrom-operating the cam; and comprises plunger 25 and the indexing parts including pawl 3| and ratchet wheel 29, cable shaft 3D, exible cable 45, worm 42, worm gear 4|, shaft 40, worm 39 and worm gear 38, splined to the cam shaft. Between the diaphragm Il and the cam shaft H the necessary operating force is transmitted through the first mentioned chain of connected Darts whereas the second chain merely applies a corrective adjustment when necessary without the contacting second chain to each other at any point and thus without influence one on the other.

I claim:

1. In a brake, the combination of a cam for operating the brake shoes, a cam shaft for actuating the cam, an arm mounted to turn about the shaft for rocking the same and thus actuate the cam, a worm gear fast on theshaft and housed within the arm, a worm shaft provided with a worm journalled in the arm and in driving engagement with the worm gear to adjust the same rotatively relative to the arm, a reducing gear drive journalled in the arm and including a second large worm gear secured to the worm shaft, a second worm shaft meshing with said large worm shaft, power means including a reciprocating diaphragm connected to the arm to rock the same and thus actuate the cam, indexing means normally inoperative while the reciprocating diaphragm moves back and forth in its travel to cause the cam to operate the brake, said Y.

indexing means operatively controlled and energized by a movement of the reciprocating diaphragm beyond that required to rock the arm and operate the brake and a flexible driving connection between said indexing means and the second worm shaft.

2. The combination with a cam controlled brake including a cam shaft and mechanism at all times operative to rock the cam shaft to cause the brake to function, said mechanism including a fixed casing having therein a pneumatically powered diaphragm, a chain of connected parts between the diaphragm and the cam shaft, including a main plunger actuated in one direction by the diaphragm, projecting to the outside of the casing and spring biased to return in the opposite direction, an arm loose on the cam shaft to rock about the same as a fulcrum and having a tail end pivotally connected to the projecting part of the plunger, a worm journalled in the head and a large gear fixed to the cam shaft and meshing with the worm, of a unit constituting an attachment to the brake including an indexing casing provided with means for detachably connecting the same to the outside f the fixed casing to become a xed part of the brake, cam adjusting means including indexing means, said indexing means including an indexing plunger slidably mounted in the indexing casing, projecting therefrom into the rst main casing through an opening provided therefor and disposed in the path of movement of the diaphragm, a one-way ratchet wheel contained in the indexing casing, rotated step-by-step by the indexing plunger when the plunger moves for an abnormal distance on its cam operating movement, a driving connection between the ratchet and the worm for indexing the worm and thus the cam over an arc controlled by the rotation of the ratchet, said driving connection including a flexible drive shaft having a casing fixed at one end to the indexing casing and at its other end to the rocking head.

3. In a brake mechanism, the combination of two spaced apart relatively movable structures, one of said structures formed of two units, one

of said units constituting afain casing provided with means for mounting it xedly in place and provided therein with a reciprocating main plunger and the other unit including an indexing casing providedv with means for mounting it fixedly in place and the other structure including a brake actuating shaft, an arm normally loose on the shaft, a worm shaft journalled in the arm and a worm-forming reducing gear drive between the worm shaft and the brake actuating shaft, a chain of connected parts between the reciprocating plunger and the arm to rock the shaft in the normal operation of the brake mechanism, said indexing casing having a part thereof forming a guide tube, indexing mechanism within the indexing casing including an indexing plunger slidably mounted in the guide tube and operatively controlled by an abnormal movement of the main plunger and said indexing mechanism including a feed pawl and a ratchet' wheel actuated by the pawl and a flexible drive bridging the space between the two relatively movable structures for transmitting rotary movement of the ratchet wheel to the worm forming the reducing gear drive.

4. In a device of the class described, the cornbination with a shaft, an arm mounted on the shaft for rocking movement and operatively connected for turning the shaft, a source of pneumatic power, a casing fixed in place and provided 4therein with a diaphragm powered from said source, means actuated by the diaphragm and connected to the arm to turn the shaft in the normal operation of the device, and mechanism carriedby the arm for varying the relation of the arm to the shaft, of means forming a power transmission energized from said source including a control therefor carried by the fixed casing and provided with a plunger disposed in the path of swing of the diaphragm, controlled by an abnormal movement of the diaphragm and operatively connected to said varying mechanism to cause it to function and Said power transmission means including a flexible power transmitting element f connected at one end to the fixed casing and at its other end to the rocking arm to transmit power from said control to said varying mechanism on said rocking arm in all operative positions of the arm.

5. The combination with brake mechanism including a brake drum, brake shoes for engaging the drum, a cam and cam shaft for expansively distending the shoes into a clutching engagement with the drum, pneumatically actuated mechanism for actuating the cam shaft including a casing provided with a diaphragm dividing theY casing into a pressure chamber and a mechanismcontaining chamber, a chain of connected parts between the diaphragm and the cam shaft, said chain having a fixed length at all times and including at one end a worm gear on the cam shaft and a worm engaging the worm gear and at its other end a spring-loaded plunger intruding into the casing and having a head located in the mechanism containing chamber and engaged by the diaphragm on its braking stroke, said chain reacting on the diaphragm when the shoes bear on the drum to limit its advance on its braking stroke, of metering mechanism energized from the diaphragm and at one end operating on the worm automatically to take up slack in the chain and thus insure the engagement of the shoes with the band even in the presence of slack, said metering mechanism including a power-receiving index` annees plunger extending para11e1 to, spaced from and independent of mehe'aded plunger extending into the mechanism-eontaining chamber normally spaced from the head to provide a preset clear*- ance therebetween as the head is moved by the diaphragm on its normal braking stroke, 'said plunger being spring-loaded and biased to proect towards the diaphragm, disposed in the path of movement of and engaged by the head t'o cause the metering mechanism to function whenever the head is moved by the diaphragm any distance in excess of that distance necessary to take said clearance.

6,. In combination with a brake system complete per se and including a drum, shoes', a spring acting 'on the shoes biased to move them into an inoperative, unclutched position and a cam for moving the shoes against the resistance 'of said spring into clutching engagement with the brake band, a pneumatic power device including a swinging diaphragm and a fiXedly-coupled chain of connected parts between the diaphragm and the Cam, operative to function normally on 'a powered swing of the diaphragm in one direction, a spring supplementing the spring acting on the shoes for swinging the diaphragm in the opposite direction, said diaphragm being limited in its amplitude of swing on its powered stroke by the movement of the shoes into th-eir final braking position, and which chainv of parts as Well as the brake band and shoes is liable to develop a slacktherein during use thus permitting an additional extent of amplitude of swing of the diaphragm on its working stroke before the brake functions, of an attachment to the system including normally inoperative readjustment mechanism' connected to a part of the chain to take up the slack there'- in, said mechanism including a plunger control therefor disposed in the path of swing' of the diaphragm, a spring acting thereon and biased to move the same in the direction towards the diaphragm to assist its spring and the shoe spring to return the diaphragm to its normal inoperative position, said. plunger control spaced beyond the normal amplitude of swing of the diaphragm anddisposed to be engaged by the diaphragm and moved thereby against the resistance 4of its load-V ing spring when the diaphragm develops an abnormal amplitud of swing to cause thereadjustment mechanism to function automatically'as an incident of an ove`r-trave1 of ther diaphragm.

7. The combination of a brakeassernbly includ'- ing a mechanical brake, a pneumatically ener'- gized power unit formed of a main casing, a diaphragm dividing the casing`r into two separate parts, one part forming a pressure chamber and the' other part a mechanism-containing chamber, and a chain of xedly-connected parts connecting the diaphragm with the brake and operative to cause the brake to function when pressure is ade' mitted to the pressure chamber, said diaphragmTv oiifl 'a'd relatively lSmall fhplf Of "Silvi-ng 'When th Chail 'S Substantially f'e Of slack I"and a greater va'militude of swing when there S Slack in the chain, pneumatical-ly-O'W'- e'd A-lyhlsl'ial'sln Operating 'the chain to take up automatically any slack therein, anda cfontro for regulating the transmission of power therethrough, vsaid control including a control casing carried by the main casing, a spring-loaded plunger guide in the control casing and having its advance end located in the mechanism-con; trolling chamber in position normally spae'dfrom fh diaphragm When 0n its nrlnal and relativly small amplitude of swing and in position to b v'e by the diaphragm when 011 its greater fnpl'itude f Swing, thereby to Cause the take-up I'nhnish t function.

8; an article f manufacture, an attachment for4 use with a brake mechanism complte per s and which mechanism includes a Inotor having I'ni asig with a pl'leu'lnat'cally atuatd dia;- phragm therein, a cam and an associated ri shaft for actuating the brake mechanism; an arm swingingoii the cam shaft, a worm gear on the Can Shaft, a Woi jou'rhald in the arrn anti meshing with the worm gear, said worm gear and worm controlling the relation of cam shaft and arm, and a connection between the diaphragm and the arni to' o'ck the same and thus cause the brake rnhan'sn to functl, Said att/anhinl forming a nete'ring device for acting on th worin t'o' vary the relation between the cam shaft and arm, s'aid metering device including index` casing fashioned to be detachably attached to th main casing', a control for the' metering device ircluding a spring-loaded plunger slidabl7 mounted in the index casing and disposed to intrude into the main casing and to be located in the path' of movement of the diaphragm when moving on its braking stroke, a reducing driving connection pro'- vided with means forl securing it to' thev arm and in driving relation to the Worm to vary the rela--A tion of the cam shaft to the arm as an incident (if diaphragm movement and a flei'iible pbwr trafrjisni'ssiorrv between the control in the index` 

